The short answer
Chimney waterproofing protects brick and mortar from rain and freeze-thaw damage by sealing the crown and flashing and applying a breathable, masonry-specific water repellent. It works best after an inspection confirms where water is entering and after any cracked or failing areas are repaired.
Water causes more slow, expensive damage to a masonry chimney than fire does. Rain soaks into porous brick and mortar, and in winter that moisture freezes, expands, and pushes the masonry apart a little more each cycle. Over time you get crumbling joints, flaking brick faces, a cracked crown, rusted dampers, and water stains on the ceiling or wall next to the fireplace. All Star Chimney Sweep waterproofs chimneys for homeowners in Brooklyn and nearby communities. We start by finding where the water is getting in, fix the entry points that a sealer alone can't fix, and then apply a breathable water repellent made for masonry. The goal is a chimney that sheds rain from the outside while still letting trapped moisture escape.
Signs you need it
Moisture problems usually show up inside the house before anyone climbs onto the roof. If you notice any of these, the chimney is likely taking on water and should be looked at before the next round of freezing weather.
- Water in the firebox, or puddles and drips after heavy rain
- White, chalky staining on the brick, which is mineral salt left behind as water moves through the masonry
- Brick flakes, mortar sand, or tile fragments collecting in the firebox
- A stronger smoke or creosote smell on damp, humid days, since moisture mixes with deposits in the flue
- Stains, peeling paint, or soft drywall on the walls or ceiling around the chimney
- A rusted damper, firebox grate, or chimney cap
What's included
Waterproofing is more than spraying the outside of the chimney. A sealer won't stop water coming through a cracked crown or a gap in the flashing, so we deal with those first. Every visit includes the following:
- Inspection of the chimney exterior, crown, flashing, cap, and the firebox and damper inside
- Camera inspection of the flue when water damage to the liner or tiles is suspected
- Cleaning the masonry surface so the repellent can soak in evenly
- Sealing small cracks in the chimney crown with a crown sealant
- Checking and resealing the flashing where the chimney meets the roof
- Applying a vapor-permeable water repellent made for brick and mortar
- Recommendations for a chimney cap if the flue is open to rain
- A written summary of what we found, what we did, and anything that still needs repair
How our crew works on the roof and in your home
Most waterproofing happens on the roof. We set up safe access, inspect the crown and flashing up close, and clean loose dirt and growth off the brick. The repellent goes on at low pressure so it saturates the masonry instead of running off. We use breathable products, not paint or film-forming coatings, because sealers that trap moisture inside the brick can make spalling worse.
Inside, we lay drop cloths from the door to the fireplace and keep a HEPA vacuum running whenever we open the damper or check the firebox. If a camera inspection is needed, we run it up the flue to look for cracked tiles, gaps in the mortar joints, and water staining you can't see from below. When soot or creosote buildup is part of the problem, we can clean the flue with rotary brushes during the same visit. We clean up before we leave.
Time for your annual chimney check?
The standards we follow
The NFPA 211 standard calls for chimneys, fireplaces, and vents to be inspected once a year. Chimney professionals use three inspection levels: Level 1 when nothing has changed, Level 2 when the system changes, such as a new appliance, a switch of fuel, or a home sale, and Level 3 when a hidden hazard can only be reached by opening part of the chimney or building. A routine waterproofing visit usually goes with a Level 1 inspection. Serious water damage may call for a Level 2 camera inspection.
Moisture inside the flue matters too. When a New York City building converts its boiler from oil to gas, the chimney has to be evaluated, and a new liner is often needed because gas exhaust produces acidic condensate that can corrode a masonry flue. If your chimney vents a converted boiler, we'll check the liner as part of the visit.
What affects the price
Every chimney is different, so we quote after we've seen it. The main factors are:
- Chimney height, roof pitch, and how easy the roof is to reach
- Overall size of the chimney and how much masonry needs treatment
- Condition of the crown, flashing, and mortar joints
- Whether repairs such as repointing, crown rebuilding, or new flashing are needed before sealing
- Whether a camera inspection of the flue is needed
- Fuel type and liner condition, especially for chimneys serving gas or converted oil appliances
- Whether a new chimney cap is needed
How a visit works
When you contact us, we'll ask what you've noticed and how the chimney is used. A certified technician arrives at the scheduled time, protects the work area inside, and inspects the chimney from the firebox to the crown. Before starting any work, we walk you through what we found and what we recommend, including any repairs that should come before waterproofing.
Repellent needs dry masonry and mild temperatures, so we schedule the application around the weather. Many owners book in spring or early fall. New York City's heat season runs from October 1 through May 31, so getting the chimney sealed and inspected before October means it's ready when the heat comes on. After the work, you get a written summary and a reminder of when the next annual inspection is due.
